The present invention relates to a surface discharge AC driving plasma display panel, and more particularly, to a structure for aligning the positions of the components of the plasma display panel upon its assembly.
In recent years, a surface discharge AC driving plasma display panel has drawn considerable attention as a color display device having a large area and a small thickness, and attempts have been made to popularize the device.
FIG. 6 is a plan view schematically showing the cell structure of a conventional surface discharge AC driving plasma display panel. FIG. 7 is a cross-sectional view taken along the line Vxe2x80x94V of FIG. 6. FIG. 8 is a cross-sectional view taken along the line Wxe2x80x94W of FIG. 6.
Referring to FIGS. 6-8, on the back surface of a front glass substrate 1, which is a display surface of the plasma display panel, a plurality of row electrode pairs (Xxe2x80x2, Yxe2x80x2), a dielectric layer 2 covering these row electrode pairs (Xxe2x80x2, Yxe2x80x2), and a protection layer 3 made of MgO and covering the back surface of this dielectric layer 2 are provided in this order.
Each of the row electrodes Xxe2x80x2, Yxe2x80x2 is composed of transparent electrodes Xaxe2x80x2, Yaxe2x80x2 made of a transparent conductive film, such as ITO, having a large width, and bus electrodes Xbxe2x80x2 Ybxe2x80x2 made of a metal film having a narrow width for compensating for the electric conductivity of the transparent electrode Xaxe2x80x2, Yaxe2x80x2.
These row electrodes Xxe2x80x2 and Yxe2x80x2 are disposed alternately with a discharge gap gxe2x80x2 therebetween in the column direction, and each row electrode pair (Xxe2x80x2, Yxe2x80x2) constitutes one line (row) L of the matrix display.
On a rear glass substrate 4, which faces the front glass substrate 1 through a discharge space Sxe2x80x2 filled with a discharge gas, a plurality of column electrodes Dxe2x80x2 is arranged to extend in a direction perpendicular to the row electrode pairs Xxe2x80x2, Yxe2x80x2. Belt-shape partitions 5 are formed between the column electrodes Dxe2x80x2 so as to extend in parallel with each other. Fluorescent layers 6 of three colors, R, G, B, are formed to cover the side surfaces of the partitions 5 and the column electrodes Dxe2x80x2.
Thus, the discharge space Sxe2x80x2 is defined by the partitions 5, and thereby discharge cells Cxe2x80x2 constituting respective unit luminous regions are formed at intersections of the column electrodes Dxe2x80x2 and the row electrode pairs (Xxe2x80x2, Yxe2x80x2) in respective display line L.
The above-mentioned surface discharge AC driving plasma display panel displays images in the following manner. First, through addressing operation, electric discharges are selectively effectuated between the row electrode pairs (Xxe2x80x2, Yxe2x80x2) and the column electrodes Dxe2x80x2 at the respective discharge cells Cxe2x80x2, thereby distributing lightening cells (discharge cells in which wall charges are formed in the corresponding dielectric layer 2) and light-out cells (discharge cells in which wall charges are not formed in the corresponding dielectric layer 2) on the panel in correspondence with an image to be displayed.
After this addressing operation, a discharge-maintaining pulse is applied alternately to the row electrode pairs (Xxe2x80x2, Yxe2x80x2) for all the display lines L at once. Every time this discharge-maintaining pulse is applied, surface discharge is generated at the lightening cells.
This way, ultraviolet rays are generated at the lightening cells by surface discharge, and the fluorescent layers 6 of R, G, B in the discharge cells Cxe2x80x2 are respectively excited to emit light, thereby forming the image to be displayed.
The plasma display panel having the above-mentioned structure is assembled by superimposing the front glass substrate 1 having the row electrodes Xxe2x80x2, Yxe2x80x2, dielectric layer 2, and protection layer 3 formed thereon onto the rear glass substrate 4 having the column electrodes Dxe2x80x2, partitions 5, and fluorescent layers 6 formed thereon.
At the time of this assembly, it is necessary to ascertain an offset between a pattern of the row electrodes Xxe2x80x2, Yxe2x80x2 formed on the front glass substrate 1 and partitions 5 formed on the rear glass substrate 4. This evaluation is performed by detecting the amount of a deviation of an alignment-use mark on the rear glass substrate 4 from the pattern of the row electrodes Xxe2x80x2, Yxe2x80x2 (positional relationship between the row electrodes and the partitions) in the condition where the front glass substrate 1 is temporarily fixed to the rear glass substrate 4 by clips in advance of cementing these substrates together.
Such evaluation is necessary because the deviation (alignment error) between the front glass substrate 1 and the rear glass substrate 4 causes a degradation in the luminance and a decrease in the power margin. Once the deviation is detected, the deviation is eliminated by applying a counter-offset.
Here, in the conventional surface discharge AC driving plasma display panel described above, as shown in FIG. 8, the fluorescent layers 6 are formed even on the side surfaces of the belt-shape partitions 5 in order to increase the luminous areas in the discharge cells Cxe2x80x2, thereby increasing the luminance of the display screen. Nonetheless, if the resolution of the screen is increased by reducing the size of each discharge cell Cxe2x80x2, the surface areas of the fluorescent layers 6 are accordingly reduced, and the resultant luminance decreases, which is a drawback.
Furthermore, if the pitch of the row electrode pairs (Xxe2x80x2, Yxe2x80x2) is narrowed to achieve a higher resolution of the screen, discharge interference occurs between the discharge cells Cxe2x80x2 adjacent in the vertical direction, increasing a likelihood of misdischarge, which is another drawback.
In light of the above problems, the present applicant has previously proposed a novel surface discharge AC driving plasma display panel shown in FIGS. 9-11.
In this plasma display panel, a plurality of row electrode pairs (X, Y) is parallely arranged on the back surface of a front glass substrate 10, which is the display face, in such a way as to extend in the row direction of the front glass substrate 10 (the right and left direction in FIG. 9).
Each of the row electrodes X is composed of transparent electrodes Xa, each of which is formed to have the shape of the letter xe2x80x9cTxe2x80x9d and is made of a transparent conductive film, such as ITO, and a bus electrode Xb made of a metal film, which extends in the row direction of the front glass substrate 10 and is connected to the narrow base end part of each transparent electrode Xa.
Similarly, each of the row electrodes Y is composed of transparent electrodes Ya, each of which is formed to have the shape of the letter xe2x80x9cTxe2x80x9d and is made of a transparent conductive film, such as ITO, and a bus electrode Yb made of a metal film, which extends in the row direction of the front glass substrate 10 and is connected to the narrow base end part of each transparent electrode Ya.
These row electrodes X and Y are alternately arranged in the column direction of the front glass substrate 10 (the vertical direction in FIG. 9). Each of the transparent electrodes Xa and Ya arranged along the respective bus electrodes Xb and Yb extends towards the corresponding paired row electrode so that the sides of the wider parts of the paired transparent electrodes Xa and Ya face each other through a discharge gap g having a predetermined distance.
Each of the bus electrodes Xb, Yb is formed of a black conductive layer Xbxe2x80x2, Ybxe2x80x2 on the display surface side and a primary conductive layer Xbxe2x80x3, Ybxe2x80x3 on the back side in a double-layered structure.
A black light absorption layer 17 is formed on the back surface of the front glass substrate 10 between the row electrode pairs (X, Y) adjacent in the column direction i.e., between the bus electrode Xb and the-bus electrode Yb.
Further, a dielectric layer 11 is formed on the back surface of the front glass substrate 10 to cover the row electrode pairs (X, Y). On the back surface of the dielectric layer 11, elevated dielectric layers 11A protruding from the back side of the dielectric layer 11 are formed at positions facing the bus electrode Xb and the bus electrode Yb, which are adjacent to each other and belong to the row electrode pairs (X, Y) adjacent, and at positions corresponding to a space between such bus electrodes Xb and Yb. The elevated dielectric layers extend in parallel with the bus electrodes Xb, Yb.
Also, a protection layer 12 made of MgO is formed at the back side of these dielectric layer 11 and elevated dielectric layers 11A.
On the other hand, on a display-side surface of the rear glass substrate 13, which is disposed in parallel with the front glass substrate 10, column electrodes D are arranged so as to extend in a direction perpendicular to the row electrode pairs (X, Y) (column direction) at positions where the transparent electrodes Xa and Ya of the respective row electrode pairs (X, Y) face each other. The column electrodes D are disposed in parallel with each other with a predetermined space therebetween.
Further, white dielectric layers 14 are formed on the display-side surface of the rear glass substrate 13 to cover the respective row electrodes D, and a partition 15 is formed on these dielectric layers 14.
This partition 15 is formed of vertical walls 15a, which extend in the column direction at spaces between the column electrodes D which are disposed in parallel with each other, and horizontal walls 15b, which extend in the row direction at the positions facing the elevated dielectric layers 11A, to construct a lattice shape.
Accordingly, a discharge space between the front glass substrate 10 and the rear glass substrate 13 is partitioned by this lattice-shape partition 15 in accordance with the regions where the paired transparent electrodes Xa and Ya in the respective row electrode pairs (X, Y) face each other, thereby forming respective rectangular-shape discharge cells C.
The side surfaces of the partition 15 which face the discharge space S are formed to have a substantially white color (i.e., light reflective layer).
The display-side surface of the vertical wall 15a of the partition 15 is not in contact with the protection layer 12 (see FIG. 11), and there exists a gap r therebetween. However, the display-side surface of the horizontal wall 15b is in contact with a portion of the protection layer 12 which covers the elevated dielectric layer 11A (see FIG. 10) so that the discharge cells C adjacent in the column direction are isolated, repectively.
In the plasma display panel having the structure above, as in the case of the conventional art, when the front glass substrate 10 and the rear glass substrate 13 are superimposed on each other upon its assembly, a deviation between patterns of the both substrates needs to be ascertained and eliminated before cementing the substrates together.
However, this newly proposed plasma display panel has the following draw back in conducting such a procedure. As seen from FIGS. 9-11, when viewed from the side of the front glass substrate 101 the horizontal wall 15b of the partition 15 is positioned at the back side of the black conductive layers Xbxe2x80x2, Ybxe2x80x2 of the bus electrodes Xb, Yb and at the back side of the light absorption layer 17 between these bus electrodes Xb, Yb. Thus, it is difficult to ascertain the amount of the deviation of the partition 15 relative to the front glass substrate 10 in the column direction by observing an alignment mark formed on the horizontal wall 15b. 
The present invention is devised to solve the drawbacks which occur upon assembly of a plasma display panel, as described above.
An object of the present invention is to facilitate evaluation of the amount of a deviation in a column direction between a front substrate and a rear substrate upon assembly of a plasma display panel, a discharge space of which is partitioned by vertical walls and horizontal walls of a partition, thereby improving alignment accuracy between the front substrate and the rear substrate and the performances of the result ant plasma display panel.
To achieve the object above, in a first aspect of the present invention, there is provided a position alignment structure for a plasma display panel comprising a front substrate and a rear substrate opposite to the front substrate with a discharge space therebetween, said front substrate having thereon a plurality of row electrode pairs extending in a row direction and arranged in parallel in a column direction, each of the plurality of row electrode pairs defining a corresponding display line, said rear substrate having thereon a plurality of column electrodes extending in the column direction and arranged in parallel in the row direction, the column electrodes defining unit luminous regions in the discharge space at their respective intersecting positions with the row electrode pairs, a position alignment structure for the plasma display panel comprising: a partition on said rear substrate, having vertical wall parts extending in the column direction and horizontal wall parts extending in the row direction to partition the discharge space between said front substrate and said rear substrate in the column and row directions in accordance with the unit luminous regions; and a position alignment-use rib formed on said rear substrate and positioned at an outside of a display region of the plasma display panel for detecting a position of said front substrate relative to said rear substrate.
According to the first aspect of the present invention, the discharge space between the front substrate and the rear substrate is partitioned into the respective unit luminous regions by the partition having the vertical wall parts extending in the column direction and the horizontal wall parts extending in the row direction.
Upon assembly of this plasma display panel, the front glass substrate having the row electrode pairs and other structures formed thereon is superimposed on the rear glass substrate having the partition, the position alignment-use ribs; and other structures formed thereon, and they are temporarily fixed to each other. Then, distances between the position alignment-use rib positioned at the outside of the display region of the plasma display panel and particular structures formed on the front substrate, such as the bus electrodes extending in the row direction, which constitute the row electrode pair, are measured to determine whether the measured distances are different from predetermined values, thereby detecting positional deviations between the front substrate and the rear substrate.
This way, according to the first aspect of the present invention, upon assembly of the plasma display panel, position alignment between the superimposed front and rear substrates can be performed using the position alignment-use rib formed on the rear substrate at the outside of the display region of the plasma display panel. Therefore, even where the horizontal wall parts of the partition of the rear substrate superimposed in this manner cannot be observed from the side of the front substrate, the amount of the positional deviation between the front substrate and the rear substrate in the column direction can easily be ascertained at the time of assembly, thereby improving accuracy in position alignment between the front substrate and the rear substrate.
As a result, the performances of the resultant plasma display panel can be improved.
In a second aspect of the present invention, to achieve the object above, the position alignment structure for the plasma display panel is characterized in that, in addition to the construction of the first aspect above, the position alignment-use rib on the rear substrate is formed in a space positioned at the outside of the display region of the plasma display panel among spaces defined by the partition.
According to the second aspect of the present invention, position alignment of the front substrate relative to the rear substrate is performed using the position alignment-use rib formed in the space positioned at the outside of the display region of the plasma display panel among spaces defined by the partition.
In a third aspect of the present invention, to achieve the object above, the position alignment structure for the plasma display panel is characterized in that, in addition to the construction of the second aspect above, the position alignment-use rib is formed at a position separated from the opposing horizontal wall parts of the partition defining the space having the position alignment-use rib therein by respective distances being substantially the same at both sides.
In this position alignment structure for the plasma display panel according to the third aspect of the present invention, the position alignment-use rib is formed at the position separated from both sides of the horizontal wall parts of the partition partitioning the space by respective distances which are substantially the same at the both sides. Thus, when position alignment between the front substrate and the rear substrate is performed, the position alignment-use rib is aligned to be located at a position separated by an equal distance from a particular pair of structures which are formed on the front substrate at positions which would be, in alignment, symmetrical in the column direction with respect to the position alignment-use rib, such as bus electrodes constituting an row electrode pair.
Thus, according to the third aspect, by detecting the difference in the distances from the position alignment-use rib to the particular pair of structures on the front substrate, which are located on both sides with respect to the position alignment-use rib in the column direction, the positional deviation between the front substrate and the rear substrate can easily be ascertained.
In a fourth aspect of the present invention, to achieve the object above, the position alignment structure for the plasma display panel is characterized in that, in addition to the construction of the first aspect above, a position of the position alignment-use rib is set such that if the position alignment-use rib is translated in the row direction, the resulting position would be between two electrodes constituting the row electrode pair.
According to the fourth aspect of the position alignment structure for the plasma display panel of the present invention, when the position alignment of the front substrate and the rear substrate is performed, the position of the alignment-use rib translated in the row direction coincides with the position between two electrodes constituting the row electrode pair. Accordingly, position alignment between the front substrate and the rear substrate can easily conducted using even this relative positional relationship between the position alignment-use rib and the row electrode pair disposed within the display region of the plasma display panel.
In a fifth aspect of the present invention, to achieve the object above, the position alignment structure for the plasma display panel is characterized in that, in addition to the construction of the first aspect above, the partition and the position alignment-use rib are formed by patterning a glass layer in accordance with a predetermined pattern, the glass layer being formed on the rear substrate at a side facing the front substrate and being formed of a glass having a low melting point.
According to the fifth aspect of the position alignment structure of the present invention, the partition and the position alignment-use rib are simultaneously formed on the rear substrate by patterning. Thus, positioning of the position alignment-use rib with respect to the partition can be secured, and the accuracy in position alignment between the front substrate and the rear substrate can be improved.
In a sixth aspect of the present invention, to achieve the object above, the position alignment structure for the plasma display panel is characterized in that, in addition to the construction of the first aspect above, the position alignment-use rib on the rear substrate extends outwardly from the vertical wall part positioned at an end of the partition in a direction parallel to the horizontal wall parts, the position alignment-use rib being formed integrally with the partition.
According to the sixth aspect of the position alignment structure for the plasma display panel of the present invention, the position alignment of the front substrate relative to the rear substrate is conducted using the position alignment-use rib which is formed integrally with the partition in such a way as to extend outwardly from the vertical wall part positioned at the end of the partition.
In a seventh aspect of the present invention, to achieve the object above, the position alignment structure for the plasma display panel is characterized in that, in addition to the construction of the sixth aspect above, the position alignment-use rib is formed at a substantially center position of the vertical wall part of the partition.
According to the seventh aspect of the position alignment structure for the plasma display panel of the present invention, the position-alignment rib is formed at the substantially center position of the vertical wall part of the partition. Thus, when position alignment between the front substrate and the rear substrate is performed, the position alignment-use rib is aligned to be located at a position separated by an equal distance from a particular pair of structures which are formed on the front substrate at positions what would be, in alignment, symmetrical with respect to the position alignment-use rib in the column direction, such as bus electrodes constituting an row electrode pairs.
Thus, according to the seventh aspect, by detecting the difference in the distances from the position alignment-use rib to the particular pair of structures on the front substrate, which are located on both sides of the position alignment-use rib in the column direction, the positional deviation between the front substrate and the rear substrate can easily be ascertained.